Laying Flagstone

Sand Installation

1. Level the base. Set temporary or permanent edgings, their top surfaces approximately one stone thickness below the finished grade. Place dampened sand between guides; screed it smooth with a straight piece of lumber. Tamp the sand then re-screed again, as necessary.
2. Set stones in sand base starting from a corner. Scoop out or fill in sand as necessary to compensate for variations in stone thickness. Tap stones into place with a mallet or piece of wood. The use of a long level over several stones will help you to maintain grade. If you’re using irregularly shaped stones, lay them out in advance, adjusting pattern and joint spacing, as needed.
3. Sand the joints. Spread fine sand over the surface of the finished paving. Make sure the sand is completely dry and then sweep it into the joint. Use a fine spray to wet the finished paving down; this helps to settle the sand.

Dry Mortar Installation

4. Follow steps 1 and 2. Mix dry cement and sand in a 1:4 ratio and spread over the surface, brushing it into the open joints. Carefully sweep the mixture off the stone surface.
5. Tamp the mortar. Use a piece of 1” thick wood to tamp the dry mix into the joints; this improves the bond. Carefully sweep all dust off surface of stone before going on to the next step, as it may stain.
6. Wet the surface; using an extremely fine spray so as not to splash mortar out of the joints, wet down the paving. Don’t allow pools to form. Over the next 2 to 3 hours, wet the paving periodically, keeping it damp. Tool the joints when the mortar is firm enough. After a few hours you can scrub the unit faces with a natural bristle soft brush to remove mortar stains, burlap also works well. Allow the damp surface to dry slowly to ensure proper curing.

Wet Mortar Installation

7. On your existing concrete slab, arrange stones in a pleasing pattern, allowing minimum space for mortar joints. To trim a stone, lap it over its neighbor and mark a trim line. To cut, score the line with a brick-set or stonemason’s chisel, prop the edge to be cut off on a wood scrap, and strike the scored line with a brick-set (or stonemason’s chisel) and a softheaded steel hammer.
8. Set stones. Trowel enough 1:3 ratio cement-sand mortars onto the slab to make full mortar beds for one or two stones at a time. Keep the mortar stiff enough to support the stones. Stones should be clean and dry to ensure a good bond. (To save time, we suggest cleaning your stone to remove all dirt and dust and make sure the stone is dry prior to starting your project).
Set each stone firmly in place and bed it by tapping with a rubber mallet. Using a straightedge and level will help to maintain an even surface.
9. Let the mortar set for 24 hours, then pack mortar between the stones. To improve workability, add 1 part fireclay to the mortar if desired. Do not use lime as it may leave stains on natural stone. Finish by smoothing the joints with a trowel.
Clean up any spills with a sponge and water, clean as you go. This is important, as muriatic acid washes, commonly used to clean cured masonry, can be harmful to natural stone.